BEAUFORT, JOHN, first Earl of Somerset and Marquis of Dorset and of Somerset (1373?–1410), born about 1373, was the eldest son of John of Gaunt [see John, 1340–1399], by his mistress, and afterwards his third wife, Catherine Swynford [q. v.] His younger brothers, Henry Beaufort, cardinal and bishop of Winchester [q. v.], and Thomas Beaufort, earl of Dorset [q. v.], are separately noticed, and his sister Joan was married to Ralph Neville, earl of Westmorland [q. v.] Henry IV was his half brother. The Beauforts took their name from John of Gaunt's castle of Beaufort in Anjou , where they were born, and not from Beaufort Castle in Monmouthshire. It was afterwards asserted (Ellis, Original Letters, 2nd ser. i. 154) that John Beaufort was in 'double advoutrow goten,' but he was probably born after 1372, when Catherine Swynford's first husband died; by an act of parliament passed on 6 Feb. 1397, shortly after John of Gaunt's marriage to Catherine Swynford, the Beauforts were legitimated. This act, though it did not in terms acknowledge their right of succession to the throne — did not in terms forbid it (Bentley, Excerpta Historica, pp. 152 sqq.), but when, in 1407, Henry IV confirmed Richard II's act, he introduced the important reservation 'excepta dignitate regali' (Stubbs, Const. Hist. iii. 58-9).

John Beaufort's first service was with the English contingent sent on the Duke of Bourbon's expedition against Barbary in 1390. They sailed from Genoa on 15 May of that year, and landed in Africa on 22 July. On 4 Aug. an attack was begun on El Mahadia, but after seven weeks' ineffectual siege, the English force re-embarked, reaching England about the end of September. Beaufort was knighted soon afterwards (Doyle says in 1391), and in 1394 he was serving with the Teutonic knights in Lithuania. Probably, also, he was with Henry of Derby (afterwards Henry IV) at the great battle of Nicopolis in September 1396, when the Turks defeated the Christians, and Henry escaped on board a Venetian galley on the Danube. Returning to England, Beaufort was, a few days after his legitimation, created (10 Feb. 1396-7) Earl of Somerset, with place in parliament between the earl marshal and the Earl of Warwick. He then took part, as one of the appellants, in the revolution of September 1397, which drove Gloucester from power and freed Richard II from all control (Stubbs, iii. 21). On 29 Sept. he was created Marquis of Dorset, and in the same year was elected K.G., and appointed lieutenant of Aquitaine. His was the second marquisate created in England; the creation is crossed out on the charter roll, and on the same day he was created Marquis of Somerset, but it was as Marquis of Dorset that he was summoned to parliament in 1398 and 1399, and he seems never to have been styled Marquis of Somerset. He remained in England when Richard II banished his half brother Henry of Derby, was appointed admiral of the Irish fleet on 2 Feb. 1397-8, and constable of Dover and warden of the Cinque Ports three days later; on 9 May following he was made admiral of the northern fleet.

He had thus identified himself to some extent with the unconstitutional rule of Richard's last years, and probably it was only his relationship to Henry IV that saved him from ruin on Richard's fall. He was accused for his share in Richard's acts by parliament in October 1399, and pleaded in excuse that he had been taken by surprise and dared not disobey the king's command. He was deprived of his marquisates, and became simply Earl of Somerset, but there was never any doubt of his loyalty to the new king, his half brother. He bore the second sword at the coronation on 13 Oct. 1399, was appointed great chamberlain on 17 Nov., and in January following was, with Sir Thomas Erpingham [q. v.], put in command of four thousand archers sent against the revolted earls. On 8 Nov. 1400 he was granted the estates of the rebel Owen Glendower, but was never able to take possession of them. On 19 March 1401 he appears as a member of the privy council, and four days later was appointed captain of Calais. He was sent on a diplomatic mission to France in the same year, and general suspicion having been created by the rebellion of the earls, Somerset was, on the petition of the commons, declared loyal. In 1402 the commons also petitioned that he might be restored to his marquisate, but Somerset wisely declined on the ground that the title marquis was strange to Englishmen.

During that year (1402) Somerset was actively employed. On 27 April he was sent to negotiate with the Duke of Guelders; and in June he escorted to Cologne the king's daughter Blanche on her marriage to Ludwig of Bavaria. He had been witness to Henry IV's marriage by proxy to Joan of Brittany at Eltham on 3 April, and later in the year he was sent to fetch the new queen to England. In October he was one of the lords permitted by Henry to confer with the commons on condition that this constitutional innovation was not to be taken as a precedent (Stubbs, iii. 37). He also saw some service with the fleet, capturing several Spanish ships in the channel. He seems to have taken no part in the suppression of the Percies' revolt in 1403, but on 28 Sept. he was made lieutenant of South Wales. On 13 Feb. 1403-4 he was nominated joint-commissioner to treat with France, and on 20 Oct. 1404 was appointed deputy-constable of England. Early in the same year he was one of the ministers whom Henry IV, as a further condescension to public feeling, nominated in parliament to form his great and continual council (ib. iii. 44). From 23 Dec. 1406 to 8 May 1407 he was admiral of the northern and western fleets.

Somerset, who had been in failing health for some time, died in St. Catherine's Hospital by the Tower on 16 March 1409-10 (not, as all the peerages say, on 21 March), and was buried in the Abbey church on Tower Hill (English Chron. ed. Davies, p. 37). An alabaster monument was afterwards erected to his memory in St. Michael's chapel, Canterbury Cathedral. He married, before 23 April 1399, Margaret, daughter of Thomas Holland, second earl of Kent [q.v.], and by her, who afterwards married Thomas, duke of Clarence [q.v.], had issue—three sons and two daughters. The three sons—Henry (1401-1418), John (1403-1444) [q.v.], and Edmund (1405?-1455) [q.v.]—all succeeded as earls of Somerset; John and Edmund were also dukes of Somerset. Of the daughters, Jane or Joan married James I of Scotland, and is separately noticed [see Jane, d. 1445], and Margaret married Thomas Courtenay, earl of Devon.